Flashing LED brake light circuit
Simple flashing brake light
The circuit can use to make a simple pulsating stop brake light which continuously flashes as long as the brake is applied. Here we are using a 555 astable multivibrator to generate the flashing. The working of flash brake light circuit is same as 555 flasher circuit. With the given values for R1, R2 and C1, the circuit has an ON period and OFF period of 0.125 seconds and 0.124 seconds respectively.
The LED brake light has a set of 3×3 LED bulbs, 3 parallel set of 3 series LEDs and 220 ohms resistance. The 555 IC has a maximum output current of 200mA. The output current driven by an LEDs are about 20ma – 40 ma. Here in the set, it is about 25ma. As the total current is below 100ma, the LEDs can be connected directly to the output pin of the 555IC. Also, as the brake light is not lighting for a too long the IC does not heat as much. Even though, the circuit can work fine if it kept ON for a long period.
The switch should be placed so as to activate the circuit while applying the brake. Or replace the switch with any another easy mechanism which makes an electrical contact during braking. Also, the circuit can be connected in parallel to the existing brake light. But the power rating of wire and fuse should be considered while connecting along with it.
Flash Light – Components required
Integrated circuit – IC – NE555
Resistor – R1 – 1K,R2 – 82K, R3,R4,R5- 220ohms
Capacitor – C1 – 2.2uf, C2 – 0.01uf
Diode – D1 – D9 – Red LED
Flash and Hold Brake light
In flash and hold circuit, the light does not flash continuously as like a normal flasher. Instead, the circuit flashes initially for a few seconds and then hold the ON state until the brake switch has released.
This brake light circuit consists of an additional monostable multivibrator with the above flasher circuit. In the circuit, the output of the monostable multivibrator has been connected to the base of a PNP transistor, which has connected across the capacitor C4. So, during the high state of the IC1, the Q1 is OFF. Thus the astable multivibrator generates periodic signals, which flash the LEDs. After the quasi state period of IC1, the output return to the low state. At this time the Q1 ON and it shunts the capacitor. Thus the voltage at the trigger pin becomes below 1/3Vcc and holds the ON state at the output of IC2, which is actually interrupting the working of the astable multivibrator.
The flashing time of the circuit is equal to the time period of the monostable multivibrator. So the period of flashing can be adjusted by varying the time period of the monostable multivibrator.
Brake Light – Components required
Integrated circuit – IC1,IC2 – NE555
Transistor – Q1 -BC557
Resistor – R1 – 470K, R2,R3 – 1K, R4 – 100K, R5-R7- 220ohms
Capacitor – C1 – 4.7uf, C2 – 22pf, C3,C5 – 0.01uf, C4 – 2.2uf, C6 – 220uf
Diode – D1 – D9 – Red LED